Rotary switches are often utilized for selectively establishing one or more electrical connections by turning a dial, key or knob. The knob, in turn, connects to a contact mechanism disposed in a contact compartment and responsive to rotation of the knob to move an electrical contact relative to fixed contacts.
One of the more common examples of an economical rotary switch includes a typical engine starter responsive to rotation of a keyed cylinder to complete a start circuit. The keyed cylinder provides a measure of security in selectively enabling only those persons entrusted with the corresponding key to rotate the switch elements and actuate the start circuit. The starter is typically disposed within the interior of a vehicle, thus shielded from extreme environmental conditions.
Although the implementation of a rotary switch in the confines of an automobile interior minimally exposes the contact compartment to moisture, keyed conventional switches utilized in more extreme environments associated with watercraft, snowmobiles and construction equipment are prone to malfunction due to contamination and excessive oxidation of the contacts. The contamination often arises in such vehicles because the keyway formed in the cylinder and the annular space around the key cylinder provide undesirable moisture paths leading indirectly to the switch contacts.
With the ever-increasing popularity of environmentally exposed vehicles, those skilled in the art have explored different starter switch designs to satisfy customer concerns regarding reliability and security. One proposal includes providing a relatively inexpensive rotary dynamic seal, such as an O-ring, around the key cylinder or around a circular element of a contact rotor to minimize water entry. Other economical dynamic seal designs have implemented a "boot nut" in which a flat rubber washer, having a slit to allow entry of the key, is mounted forward of the keyhole. The rubber element rotates as the key turns to provide some measure of protection.
While such proposals are somewhat beneficial for limited exposure to the elements, continuous exposure, such as through complete submersion of a personal watercraft, typically overwhelms the limited sealing capability due to the keyway moisture path. Over time, the sliding motion of the rotating shaft relative to the dynamic seal generally causes the seal to deform and fatigue, substantially compromising the effectiveness of the seal. As a result, many manufacturers implement starters without keyed mechanisms, thereby increasing the risk of theft of the vehicle.
A related proposal for addressing the problem with relatively expensive static seals involves hermetically sealing the contacts from the outside environment with a static seal. Static seals in contrast to dynamic seals, remain fixed in an unchanging orientation. U.S. Pat. No. 5,061,831 illustrates a hermetically sealed switch for storing for long periods of time. The switch includes a metallic housing separated into two airtight compartments by a flexible metallic diaphragm welded to the interior radial surface of the housing. The center of the diaphragm is welded around the periphery of a narrow metallic actuator to maintain the seal. Bounding each end of the housing are respective rotors formed with respective grooves for engaging the respective ends of the actuator. The top rotor comprises a manual selector for activating the switch. The bottom rotor includes a contact disposed opposite a contact plate that mounts a plurality of connection elements.
Operation of the hermetic switch involves rotating the selector knob to correspondingly pivot the actuator and translate the knob movement to the contact rotor. As the contact rotor turns, the contact either makes or breaks circuits with the fixed contacts. While the relatively flexible nature of the metallic diaphragm realizes a static airtight seal between the two compartments, the design anticipates a one-shot actuation for military applications.
While the hermetic switch is beneficial for its intended purposes, the metallic nature of the sealing components, coupled with the required welding steps necessary to effect airtight sealing causes the design to be undesirable from a cost standpoint for non-airtight sealing applications. Moreover, the metal to metal welds between the diaphragm and metallic housing are subject to embrittlement after substantial use, resulting in component fatigue and loss of sealing capability.
Therefore, those skilled in the art have recognized the need for an economical rotary switch for use in extreme environments and capable of preventing moisture from contaminating a contact compartment and maintaining a high level of reliability throughout many actuations over a substantial period of time. The need also exists for such a switch to allow a measure of vehicle security through keyed access. The submersible switch of the present invention satisfies these needs.